Heat insulating sheet or panel



June 24, 1958 H. J. oKowAN El'AL 2,840,500

HEAT INSULATING SHEET 0R PANEL Filed Dec. 22, 1954 I 2 Sheets-Sheet 1 INVENTORS 6 Howard JOK'oonzzlaza 7 Lovic l? berrz'rcgfiioia BY 9W, WNW

THEIR ATTORNEYS June 24, 1958 H; J. OKOOMIAN ETAL 4 HEAT INSULATING SHEET OR PANEL Filed Dec. 22, 1954 2 Sheets-Sheet 2 INVENTORJ Howard J Olf'oomz'aza Lot Lb P BY W $W,7m W

TH El R ATTORNEYS *constructionwise.

Unite Howard J. Okoomian, West Haven, and Lovic Pierce Herrington, Hamden, Conn, assignors to John B.

rates Patent Pierce Foundation, New York, N. Y., a corporation of New York Application December 22, 1954, Serial No. 476,892 8 Claims. (Cl. 15444) This invention relates to insulating sheets or panels and in general aims to provide a panel which is a highly efficient heat insulator. Ancillary objects are to provide a heat insulating panel which is flexible so that it may be bent to conform to curved surfaces, yet sufiiciently resilient that it will spring back to its original shape when the bending stress is relieved, which is made of readily available or non-strategic materials,which may be easily secured to walls, ceilings and other supports by ordinary fastening elements such as nails, staples or bolts, which is light in weight, is not too bulky being in fact nestable, is sufiiciently stiff to be easily handled, will withstand extremes of climate, is fire-resistant, will not rot or corrode in moist air or be attacked by fungi, and if necessary may be washed. All these qualities make the panel of our invention a desirable wall surface for the interiors of temporary or portable buildings such as the Army must use in many parts of the world for personnel and supplies. Other advantages of our panel arise from the fact that aluminum foil is preferably used as facing sheets for the panel in order to reflect radiant heat; this foil reflects a good deal of light also, which results in a much brighter interior for the building wherein the panels are placed as components of an interior wall. A better illuminated interior is desirable to enhance morale and to diminishthe use of artificial lights during daylight hours. Also the foil preferably has a surface such that it presents a pleasing, even a handsome appearance. The invention is also characterized by other objects and advantages.

With reference to the invention, in the case of a laminate insulating panel composed of an inner layer of insulating material (such as glass wool) and one or more outer layers of heat-reflecting sheets (such as metal foil), it has always been assumed by the prior art that the inward facing surfaces of the sheets, when in contact with filler insulation, have no important reflectivefinsulation effect, since any such effect is assumed as necessarily dissipated due to the direct heat conduction path between the inner metal surfaces afforded by filler insulation, or due to the prevention of e ection when paper or other material is in direct contact with the metal surface. This being the assumption, it was customary in the prior art, for constructional reasons, to thermally short circuit or to reduce or eliminate the heat'reflectivity of these inner sheet surfaces by coating them overall with adhesive to bond the sheets to the central layer, by placing a paper layer in direct contact with the inner sheet surfaces between the sheets and thev central layer, or by like practices.

We have found, contraryto this prior art assumption,

that the inward facin "surfaces of the heat-refiectin r g ud m ens ysheets do, in fact, add considerably to the insulating capabilities of the panel, providing that the properi recautions are taken against thermal short circuiting of these inner surfaces by heat conduction.

The case in which no thermal short circuiting (by hea. conduction) whatever would occur is that ari'angement in which the inner surfaces of the sheets are separated only by an air gap. Such arrangement;is'notjdejsirable, however, for the reason that convection currents in the air gapwould reduce insulating etliciency, andfori'th-e' 2,840,500 Patented June 24, 1958 ice In order to meet these difficulties it is necessary, in

filler between the heat-reflecting sheets. At the same time, in order to take advantage of the insulating powers of the inner sheet surfaces, it is important to keep the thermal short circuiting of these surfaces to a minimum by reducing, insofar as possible, the areas where the surfaces are directly contacted.

The amount of such direct contact is minimized in accordance with the present invention by (1) avoiding the use of paper layers or the like between the metal sheets and the central insulating layer, (2) restricting to limited areas the adhesive which bonds the sheets and central layers together, (3) using a fibrous central insulating'layer with a medium density offering a balance between a' low total contact area of the fibers with the sheets and a satisfactory constructional strength, and (4) forming a multiplicity of ridges and valleys in the panel to further reduce the contacts between the central layer fibers and the sheet inner surfaces.

It is thus seen that a panel in accordance with the invention represents an optimum balance between thefeatures increasing the insulating powers of the panel and the features desirable from aconstruction point of view. In thiseonnection it will be understood that the word panel as used herein refers generally to an insulating structure of relatively large extent in two dimensions thereof compared to the third dimension thereof. Thus,

the description of the present invention as a, panel is not to be construed as limiting the invention to structures suitable only'to perform a wall paneling function.

--The in ention will be better understood from the following description of the preferred embodiment of .the invention shown in the accompanying drawings forming a part of this specification in which:

Fig. 1 is a top plan view of a panel embodying'the invention;

Fig. 7 is a section through portions of two nested panels each having the form of Fig. 3;

Fig. 8 is a section through portions of two panels spaced apart by afabric to form a composite insulating wall. a 7

Referring particularly to the drawings, the insulating panel of the invention consists (in-either form) of three elements, viz., acore of insulating filler material of .medium or low density and two facing sheets of bright metal foil preferably aluminum foil, the two foil sheets being secured along their edges to the coreby means of anadhesive which is spread in narrow areas so as to minimizeheat transference. The filler material may beg fonexample, commercial fiberglass wool of low or G-lass wool is particularly -suitableas a core material since besides being an excellent insulatorit is'fireproof,

-;moisture resistant and resilient in flexure to impart rea the foil sheets, is of such nature that its fibers have a further reason that the arrangement is not practical W low. total area of contact with the inner surfaces of the 7 sheets r Aluminumfoil-isparticularlysuitable as a sheet material since it is a good infra-red as well as visible light reflector, resists atmospheric corrosion, is sufliciently stiff to partially maintain its own shape and is to some extent resilient in flexure, adding thereby to the resiliency of the whole panel. The last two-named properties of aluminum foil permits a lower density glass wool layer to be used to attain the advantages heretofore mentioned.

In lieu of aluminum foil, more expensive foils or sheets'having like properties, e. g.. chromium, could be used.

The fibrous core 10, in the finished and preferred form of'panel, is about 0.31 to 0.33 in. thick while the facing foil sheets 11, 12 are about 0.006 in. thick but may be as thin as 0.003 in. The entire laminate is corrugated, with the corrugations parallel and of the same dimensions, preferably of about /8 in. to A in width. By making the width of the core of about the same size or less than the length of the sides of the corrugations, the susceptibility to flexure of the presently disclosed panel is increased to panels where the opposite situation obtains.

The corrugations of the foil sheets 11, 12 preferably have their walls at angles of 90 (Fig. 3) or 60 (Fig. 6) to each other. These corrugations are of serrate form in that they present a multiplicity of sharp-angled peaks or ridges 13 alternating with valleys or depressions 14, the respective corrugations of the two sheets registering angle for angle with each other so that the centers of the valleys of one foil sheet extend toward (that is, are in the same planes as) the peaks of the foil sheet on the other side of the core 10. Thus core 10 itself is of corrugated serrate form and a substantially uniform thickness at all points. Preferably the aluminum foil of sheets 11 and 12 is crimped to present flattened waves which extend at right angles to the direction in which peaks 13 exend. These waves reflect light in two directions to improve the distribution of light reflected from the panel when the same is used to brighten a building interior. Also the waves give a striped appearance to the panel which materially enhances the appearances of the panel. The waves 15 may, however, extend parallel to the peaks 13.

It will be seen that forming the panel to have a multiplicity of folds, either as corrugations or as waves 15, reduces the amount of direct contact between the inner sheet surfaces-and the glass wool fibers, since the fibers in their distribution tend to be less concentrated at the angles of the folds. In this regard the size. of the corrugations and crimping waves of the presently described panel are believed to represent the optimum balance between the case where the folds are so numerous as to approach a fiat surface and the case where the sheet inner surfaces are, in fact, flat surfaces. Moreover, either one or both of the corrugation or crimping folds serve (as an effect independent of reduction of direct contact with the filler material) to enlarge greatly the area of inner reflective surface over that afforded by a flat sheet. Thus the folds considerably increase the radiant insulation power of the sheets. Exteriorly, such folds minimize the physical contact of the outer reflecting surfaces with any other surfaces supporting the panel when applied to, say, a building or a pipe. The reduction in exterior physical contact serves, like the mentioned reduction in interior contact, to minimize the loss of insulating power by direct solid conduction of heat and to maximize the radiant insulating effect of the outer surfaces.

A panel made as described may have a density of about 6.1 lbs. per cubic foot, an over-all thickness of about 1.05 in., and at 139 F., a conductance of 0.487 B. t. u./hr./ F./sq. ft. and a thermal resistance of 2.05 B. t. u./hr./ F./sq. ft. The Clo per inch of, glass wool (.31 in. thickness) equals 7.54 and the resistance per inch of glass wool equals 6.61 B. t. u./hr./ E/sq. ft.

To hold the glass wool core against shifting during handling of the panel, and to make an easily handled assembly or laminate, the glass wool is coated along narrow areas with polyvinyl chloride adhesive, or other adhesive, as indicated at 16, 17, 18, 19 and 20 in Fig. 1, thereby uniting the metal foil sheets to the core. These narrow areas of adhesive are preferably only about one inch wide and extend preferably along the edges of the panel and in straightlines parallel to one of the long panel edges, as shown in Fig. 1. If the panel is narrow, the intermediate adhesive area 20 may be omitted.

As stated, by bonding the glass wool layer and foil sheets together by only a few narrow bands of adhesive, the. heattransference through the panel is minimized compared with the case where the adhesive is distributed over the major portion of the reflective surface in a uniform layer. As another advantage over uniform layer distribution, an adhesive substance used to bond panels of the sort described, generally stiffens the panels where applied. Hence, by applying the adhesive in only a few narrow bands the panel is rendered more readily susceptible to resilient flexing.

The dimensions shown in Fig. l are merely illustrative; obviously the panel may have any length and width that permits convenient handling by one or two operators. The described panels may be bent as much as about an axis A as Fig. 5 shows, to accommodate the panel to curved walls. After'the bending stress has been removed, the described panel will resume its original form because of its resiliency.

Among the factors contributing to the over-all flexural susceptibility and resiliency of the panel are the following: l) the resiliency of the core itself, (2) the resiliency of the foils, (3). the relative width of the core compared to the length of the sides of the corrugations, (4) the restriction of the adhesive to only a few narrow bands.

There are at least two methods which may be followed in fabricating the described panels. The metal foil sheets may be passed over adhesive rolls or applicators to appiy the adhesive in narrow strips or areas as described and then brought into contact with a glass fiber batt, following which the assembly may be crimped to assume the corrugated form shown in Fig. 3 or Fig. 6. Such crimping will be done by power-driven rolls, as will be understood by those skilled in the art. Another method involves corrugating the glass wool core first, and then applying the metal foil with pressure to make the sheets conform to the corrugated core. This method is especially useful'with very thin foils (about .003 in.), the necessary dimensional stability of the panel being achieved through a glass wool core that has been stiffened by means of a resin. Obviously by varying the fiber diameter and the amount of binding resin, almost any degree of rigidity in the panel may be obtained. Very thin foils not only reduce the weight of the panel but also have the same insulation efliciency as heavy foils or thin sheets which are much more expensive. Of course, very thin foils are easily damaged in handling.

The following table is based on comparative tests of the described panel (sample No. 9) with other sheets and laminates (described below).

Table Conductance Thickness of Glass W001 (111.)

Resistance per inch of Glass Wool Nora-Limiting resistance for 1 in. of absolutely still air is 5.2 (Smithsonian Physical Tables, F. E. Fowle, Smithsonian Institution, 1934 1.

Sample No. 1 of the above table consisted of two layers of glass wool between which was a sheet of corrugated aluminum foil .006 in. thick attached at the tops of the corrugations to the glass Wool by polyvinyl adhesive. Sample No. 2 consisted of two sheets of corrugated aluminum foil .006 in. thick between which was a layer of glass wool adhered by adhesive to the tops of the corrugations. Sample No. 3 consisted of a sheet of corrugated aluminum foil .006 in. thick adhered by adhesive applied at the tops of the corrugations to'a layer of glass wool. Sample No. 4 was commercial glass Wool, and sample No. 5 was the same but of less thickness. Sample No. 6 was like No. 5 except that the glass wool layer on both sides had a facing of ,6, in. crimped aluminum foil adhered thereto. Sample No. 7 was merely a single sheet of corrugated aluminum foil such as was used in the laminates identified as samples 9 and 10. Sample No. 8 was like No. 7 but with different air spacing. Sample No. 9 embodied the invention herein described. Sample No. 10 was like No. 9 except the two reflective surfaces on the inside of the two aluminum foil sheets were blackened with black paint to eliminate reflectance from these surfaces. This sample also embodied the invention, even though the elimination of reflectance was a step backward.

It will be observed that sample No. 9 materially exceeded the limiting value of absolutely still air, and even sample No. 10 almost equalled such value (5.19 nearly 5.2). a

In order to make the described panel conform to a curvature or bend in a wall or ceiling it may be turnedso that the corrugations extend either horizontally or vertically. When the corrugations run horizontally, the panel may be bent in a vertical plane, while if the corrugations extend vertically, the panel may be curved in a horizontal plane. Tacks, nails, staples, etc. are easily driven through the panel, and because of its dimensional stability, comparatively few fastening'elements are needed to hold it in position, which is advantageous especially in very cold weather, when frost will build up on metallic fastening elements. When the panel is secured against a flat surface, it will touch that surface only along the sharp peaks or ridges of the corrugations, which is advantageous in greatly reducing conduction.

When shipping the panels, much space may be saved by nesting them, as will be apparent from Fig. 7. Such nested panels of two, three, or more layers, coupled together by mechanical fastening elements such as staples or by adhesive along the edges, will form insulating layers useful in various structures, e. g., refrigerators, refrigerator cars or trucks, temporary or permanent buildings, etc. This nesting feature may also be useful in closing the joints made by two abutted panels, since narrow strips (3 /2 in. or 4 /2 in. wide) cut from the panels may be placed over such joints to conceal and substantially to seal them, especially if polyvinyl adhesive or the like is used to hold the strips tightly against the joints with the corrugations of the strips nested into the corrugations of the abutted panels. This will be undersood without specific illustration.

An even more efficient insulating wall structure is shown in Fig. 8, where two panels 30, 31, exactly like the panel of Figs. 15, are spaced apart by means of a Woven or meshed fabric 32 which may be of galvanized wire, asbestos netting, or even plastic or glass fiber cloth. Adhesive or fastening elements may secure the fabric to the panels. As fabric 32 prevents contact between the reflective surfaces of the foil, and as the peaks and valleys are directly opposed, a multiplicity of reflective dead air spaces 33 are provided which would operate as a resistance in series with the panels. Fabric 32 is of course very flexible to permit bending. The principal disadvantage of the arrangement of Fig. 8 is its much greater over-all thickness as compared to the nested arrangement of Fig; 7. As more of the panels can be assembled in the same wall space, if they are nested as in Fig. '7, the latter arrangement may be preferred in some cases even though less eflicient in resistance for an equal weight of material.

From the foregoing, it is clear that our invention provides' a panel or insulating construction which is a better heat insulator than absolutely still air. The reason for the excellence of our heat-insulating panel lies in maximizing the use of the reflective principle of insulation with a fibrous filler material which reduces internal conection to a minimum without destroying the reflective insulation effect of the internal foil surfaces.

The above-described embodiments being illustrative only, it will be understood that the invention comprehends organizations differing in form or detail from the described embodiments. Also constructions according to the invention may be used not only as Wall panels, but in divers other ways. For example, a two inch diameter pipe heated to 300-700 F. would normally take an ad-' ditional inch of insulation on each side, increasing the over-all covered diameter to four inches. With an insulating jacket of a construction according to the invention, the jacket on each side would take up only 0.6 inch of diameter to reduce the over-all covered diameterof the insulated pipe to 3.2 inches.

Accordingly, the invention is not to be considered as limited save as is consonant with the scope of the following claims.

We claim:

1. A heat insulating panel comprising, a pair of bright metallic foil, heat reflecting sheets each having inner and outer heat-reflecting surfaces and each having a plurality of similar sharp angle corrugations which extend in the direction of their ridge lines normal to a plane passing through both sheets and which follow on each other in juxtaposed relation in said plane to render the crosssections of said sheets in said plane of the same sawtooth shape, said sheets being mutually separated with respective corrugations thereof registering angle for angle and with corresponding faces of registering corrugations being parallel to thereby define between said sheets an interspace having in said plane a cross-section of sawtooth shape and of an inter-sheet width less than the dimension in said plane of the face of one of said corrugations, and a layer of fibrous glass wool occupying substantially all of' said sawtooth-shaped interspace to the exclusion of air pockets therein, said glass wool layer and said sheets being bonded together to form a united panel structure. e V

2. The invention defined in claim 1 wherein the interior angles of the corrugations are about 7 3. The invention defined in claim 1 wherein the interior angles of the corrugations are about 60.

4. A panel as in claim 1 wherein the two sheets are of aluminum foil .006 inch to .003 inch thick, the faces of the corrugations being from to inch long in the said plane, and wherein the central insulating layer is of glass Wool of a thickness of about 0.3 inch.

5. A heat insulating panel comprising, a pair of bright metallic foil, heat reflecting sheets each having inner and outer heat-reflecting surface and each having a plurality of similar sharp angle corrugations of major size which extend in the direction of their ridge lines normal to a plane passing through both sheets and which follow on each other in juxtaposed relation in said plane to render the cross-sections of said sheets in said plane of the same sawtooth shape, said two sheets each having minor size ridges and valleys which run transversely to the major size corrugations of the sheets and said sheets being mutually separated with respective corrugations thereof registering angle for angle and with corresponding faces of registering corrugations being parallel to thereby define 7 between said sheets an interspace having in said plane a cross-section of sawtooth shape and of an inter-sheet Width less than the dimension in said plane of the face of one of said corrugations, and a layer of fibrous glass wool occupying substantially all of said sawtooth-shaped interspace to the exclusion of air pockets therein, said glass wool layer and said sheets being bonded together to form a united panel structure.

6. A heat insulating panel comprising, a pair of bright metallic foil, heat reflecting sheets each having inner and outer heat-reflecting surfaces and each having a plurality of similar sharp angle corrugations which extend in the direction of their ridge lines normal to a plane passing through both sheets and which follow on each other in juxtaposed relation in said plane to render the cross-sections of said sheets in said plane of the same sawtooth shape, said sheets being mutually separated with respective corrugations thereof registering angle for angle and with corresponding faces of registering corrugations being parallel to thereby define between said sheets an interspace having in said plane a cross-section of sawtooth shape and of an inter-sheet width less than the dimension in said plane of the face of one of said corrugations, a layer of fibrous glass wool occupying substantially all of said sawtooth-shaped interspace to the exclusion of air pockets therein, and adhesive material disposed between said glass wool layer and each of said sheets and distributed over the area of said panel to extend parallel to the ridge lines of said corrugations only in narrow bands adjacent the edges of said panel, and to extend transverse to said ridge lines only in narrow bands, said adhesive material bonding said sheets and layer together into a united panel structure.

7. A heat insulating panel comprising, a pair of bright metallic foil, heat-reflecting sheets each having inner and outer heat-reflecting surfaces and each having a plurality of similar sharp angle corrugations of major size which extend in the direction of their ridge lines normal to a plane passing through both sheets and which follow on each other in juxtaposed relation in said plane to render the cross-sections of said sheets in said plane of the same sawtooth shape, said two sheets each having minor size ridges and valleys which run transversely to the major size corrugations of the sheets and said sheets being mutually separated with respective corrugations thereof registering angle for angle and with corresponding faces of registering corrugations being parallel to thereby define between said sheets an interspace having in said plane a cross-section of sawtooth shape and of an intersheet width less than the dimension in said plane of the face of one of said corrugations, a layer of fibrous glass wool occupying substantially all of said sawtoothshaped interspace to the exclusion of air pockets therein, and adhesive material disposed between said glass wool layer and each of said sheets and distributed over the area of said panel to extend parallel to the ridge lines of said corrugations only in narrow bands adjacent the edges of said panel, and to extend transverse to said ridge lines only in narrow bands, said adhesive material bonding said sheets and layer together into a united panel structure.

8. A heat insulating assembly comprising a first heat insulating panel including a pair of bright metallic foil, heat reflecting sheets each having inner and outer heatreflecting surfaces and each having a plurality of similar sharp angle corrugations which extend in the direction of their ridge lines normal to a plane passing through both sheets and which follow on each other in juxtaposed relation in said plane to render the cross-sections of said sheets in said plane of the same sawtooth shape, said sheets being mutually separated with respective corrugations thereof registering angle for angle and with corresponding faces of registering corrugations being parallel to thereby define between said sheets an interspace having in said plane a cross-section of sawtooth shape and of an inter-sheet width less than the dimension in said plane of the face of one of said corrugations, and a layer of fibrous glass wool occupying substantially all of said sawtooth-shaped interspace to the exclusion of air pockets therein, said glass wool layer and said sheets being bonded together to form a united panel structure; said assembly further comprising a second heat insulating panel similar to said first panel and a flexible fabric interposed between said panels with opposite surfaces of said fabric making contact with ridge lines of the respective corrugations of said panels, said corrugation ridge lines of said two panels being in opposed relation through said fabric so that air spaces are provided between said panels.

References Cited in the file of this patent UNITED STATES PATENTS Elfving May 22, 1956 

1. A HEAT INSULATING PANEL COMPRISING, A PAIR OF BRIGHT METALLIC FOIL, HEAT REFLECTING SHEETS EACH HAVING INNER AND OUTER HEAT-REFLECTING SURFACES AND EACH HAVING A PLURALITY OF SIMILAR SHARP ANGLE CORRUGATIONS WHICH EXTEND IN THE DIRECTION OF THEIR RIDGE LINES NORMAL TO A PLANE PASSING THROUGH BOTH SHEETS AND WHICH FOLLOW ON EACH OTHER IN JUXTAPOSED RELATION IN SAID PLANE TO RENDER THE CROSSSECTIONS OF SAID SHEETS IN SAID PLANE OF THE SAME SAWTOOTH SHAPE, SAID SHEET BEING MUTUALLY SEPARATED WITH RESPECTIVE CORRUGATIONS THEREOF REGISTERING ANGLE FOR ANGLE AND WITH CORRESPONDING THEREOF REGISTERING CORRUGATIONS BEING PARALLEL TO THEREBY DEFINE BETWEEN SAID SHEETS AN INTERSPACE HAVING IN SAID PLANE A CROSS-SECTION OF SAWTOOTH SHAPE AND OF AN INTER-SHEET WIDTH LESS THAN THE DIMENSION IN SAID PLANE OF THE FACE OF ONE OF SAID CORRUGATIONS, AND A LAYER OF FIBROUS GLASS WOOL OCCUPYING SUBSTANTIALLY ALL OF SAID SAWTOOTH-SHAPED INTERSPACE TO THE EXCLUSION OF AIR POCKETS THEREIN, SAID GLASS WOOL LAYER AND SAID SHEETS BEING BONDED TOGETHER TO FORM A UNITED PANEL STRUCTURE. 